Engine starting system

ABSTRACT

A vehicle engine starting system providing solenoid-operated positive engagement of the starting pinion with the ring gear on the engine flywheel before the starting motor is energized and inertia-operated disengagement of the pinion when the engine begins to overrun the starting motor. The system has an electrical lockout which positively prevents reengagement of the pinion as long as the engine ignition switch remains closed.

I United States Patent 1191 1111 3,747,719 Ciolli 1451 July 24, 1973 [54] ENGINE STARTING SYSTEM FOREIGN PATENTS OR APPLICATIONS [75! lhvemori Donald Ciolh, Cleveland Ohio 172,512 12/1921 Great Britain 74/7 [73] Assignee: VLN Corporation, Cleveland,

Ohi Primary ExaminerMilton Kaufman Att0rney-Yount, Flynn & Tarolli [22] Filed: Nov. 20, 1970 21 App]. No.: 91,584

Related US. Application Data [57] APSTRACT D [62] Division orsei. N6. 774 962 Nov. 12 1968 Pat. N6. A veh'cle engme start'ng system Pmwdmg 3 593 operated positive engagement of the starting pinlon with the ring gear on the engine flywheel before the 52 us. 01. 74/6 Starting is energized ahd mama-Warm 51 Int. (:1. F02n 15/06 gagemeht Ph'ioh when the engine begins 5s 1 Field 61 Search 74/6, 7 R .7 A7 B the starting The System has decimal lockout which positively prevents reengagement of the [56] References Cited pinion as long as the engine ignition switch remains UNITED STATES PATENTS clmd' 1,705,938 3/1929 McGrath 14/6 3,176,525 4/1965 12 Claims, 2 Drawing Figures Rose 74/7 ENGINE STARTING SYSTEM This is a divisional of application Ser. No. 774,962, filed Nov. l2, 1968, now US. Pat. No. 3,593,697.

This invention relates to an engine starting system, particularly for the engine of an automotive vehicle.

Various engine starting systems, particularly for automotive vehicles, have been used which employ a starting motor connected to drive a pinion which is to mesh with a ring gear connected to the engine flywheel so as to start the engine. 1

One principal type of such starting systems uses solenoid-operated engagement of the pinion with the ring gear, followed by the disengagement of the pinion from the starting motor by means of an overrunning clutch once the engine begins to overrun the starting motor. This type of system has the disadvantage that the pinion continues to be rotated at high speed by the enginedriven ring gear as long as the driver continues to run the starting motor by keeping the start switch button depressed.

Another principal type of such starting systems employs an inertia-type drive for both bringing the starter motor-driven pinion into engagement with the engineconnected ring gear and disengaging them when the engine begins to overrun the starting motor. Because the starting motor is energized before engagement of the pinion. this system has the disadvantage that the pinion may be rotating relatively fast when it is brought into engagement with the ring gear because of a delay in the inertia-operated movement of the pinion toward engagemet due to dirt or other foreign matter in the inertia-operated drive. As a result, damage to the pinion and ring gear teeth or failure to bring the pinion into meshing engagement with the ring gear may occur.

A principal object of the present invention is to provide a novel and improved engine starting system which avoids these disadvantages by combining electricallyoperated positive engagement of the pinion before the starting motor is energized, inertia-operated disengagement of the pinion once the vehicle engine begins to overrun the starting motor, and positive lockout of the pinion after it has been disengaged.

Another object of this invention is to provide such an engine starting system in which the inertia-operated disengagement of the starting motor-driven pinion causes the starting motor and the solenoid to be deenergized automatically.

Another object of this invention is to provide an engine starting system having an electrical control circuit with a novel and improved lock-out for positively preventing re-engagement of the pinion as long as the ignition switch for the vehicle engine remains closed.

Further objects and advantages of this invention will be apparent from the following detailed description of a presently-preferred embodiment thereof, with reference to the accompanying drawing in which:

FIG. 1 illustrates schematically in longitudinal section the mechanical portion of the present starting system; and

FIG. 2 is a schemtaic electrical circuit diagram of the control circuit in the present engine starting system.

Referring to FIG. 1, the present engine starter comprises a rotary, longitudinally splined, axially-fixed shaft 10 which is driven by the starting motor M in FIG. 2, and a drive pinion 11 which is adapted to be driven from shaft 10 as explained hereinafter. The drive pinion I1 is shiftable axially of the shaft 10 into and out of meshing engagement with the usual ring gear 12 on the flywheel of the vehicle engine.

The drive pinion l l is splined to the outside of an annular pinion carrier 13 which surrounds the starting motor-driven shaft 10. The splined connection of the pinion 11 to the pinion carrier has a slight spiral twist or pitch which causes the pinion to turn on the pinion carrier when one moves axially with respect to the other, in order to facilitate the meshing engagement of the pinion with the ring gear 12.

At its left end in FIG. 1 the pinion carrier has a reduced diameter portion 13a on which are mounted an annular thrust plate 14 and a flanged sleeve 15. The sleeve 15 is held in place on the reduced end portion 13a of the pinion carrier by a snap ring 16. The thrust plate 14 is engaged snugly between the inner end of sleeve 15 and an annular, radially-disposed shoulder 13b on the pinion carrier. A coil spring 17 is engaged under compression between the thrust plate 14 and the drive pinion l1, urging the pinion to the right along the pinion carrier 13 for engagemnet with a snap ring 18 carried by the pinion carrier. This spring yields if the pinion is initially brought into abutting engagement with the ring gear 12 and then, after the pinion has turned on the pinion carrier enough to clear this abutting engagement, the spring forces the pinion into meshing engagement with the ring gear.

The sleeve 15 is connected through a suitable linkage, designated schematically by the dashed line 19, to the reciprocating armature 20 of a solenoid 21 provided with a conventional return spring (not shown) which normally maintains the armature 21 in an extended position (to the right in FIG. 1). The arrangement is such that, when the solenoid 21 is de-energized and its armature 20 is in its extended position, the unitary assembly of sleeve 15, plate 14, pinion carrier 13 and pinion 11 is retracted to the left along shaft 10 from the position shown in FIG. 1. to a position in which the flanged left end of sleeve 15 abuts against a brake washer 29 located in front of a wall portion28a of the stationary housing for this mechanism. When solenoid 21 is energized to retract its armature 20, the unitary assembly of sleeve 15, plate 14, pinion carrier 13 and pinion 11 is shifted to the right along shaft 10 to the FIG. 1 position, in which the pinion meshes with the engine-d'riven ring gear 12.

A drive sleeve 22 is engaged between the shaft 10 and the pinion carrier 13. This drive sleeve is splined to the shaft 10 for movement axially along the shaft and is in screw-threaded engagement with the pinion carrier by virtue of external Acme threads 23 on the drive sleeve engaging complementary internal screw threads 24 on the pinion carrier. At the left end of its screw threads 24 in FIG. 1 the pinion carrier presents radially-disposed, annular internal shoulder 25 which limits the movement of the drive sleeve 22 to the left with respect to the pinion carrier.

A disengagement sleeve 26, which rotatably receives the splined shaft 10, extends into pinion carrier 13 to provide a limit stop for the movement of the drive sleeve 22 to the right. This disengagement sleeve has its right end abutting against a flanged bushing 27 mounted 'in another wall portion 28b of the housing.

In the operation of this mechanism, to start the vehicle engine, the driver closes a start switch (34 in FIG. 2) to energize the solenoid 21, as described hereinafter,

which then shifts the pinion carrier 13, pinion 11 and drive sleeve 22 to the right along shaft I to the position shown in FIG. I, in which the pinion meshes with the ring gear 12 connected to the vehicle engine. At this time the drive sleeve 22 is positioned along the pinion carrier 13 as shown in FIG. 1, abutting against the stop shoulder 25 on the pinion carrier and spaced from the disengagement sleeve 26.

With the pinion l1 meshing with ring gear 12, the starting motor M is started and the rotation of shaft begins. The inertia or reaction force of the vehicle engine opposes the rotation of the pinion ll initially. Consequently, with the pinion 11 and pinion carrier 13 in a non-rotating condition, the rotation of shaft 10 causes the drive sleeve 22 to be forced axially against the internal shoudler 25 on the pinion carrier. When such axial force occurs, the pinion carrier 13 and pinion 11 begin to rotate in unison with the shaft 10 driven by the starting motor M, and the rotation of pinion 11 is imparted through ring gear 12 to the vehicle engine.

After the vehicle engine has been started by the driver, by closing an ignition switch (30 in FIG. 2), as described hereinafter, the engine will reach a speed such that the ring gear 12 connected to the engine flywheel will begin to run faster than the speed imparted to the pinion 11 by the starting motor M. Consequently, gear 12 will cause the pinion 11 and pinion carrier 13 to begin to rotate faster that shaft 10 and drive sleeve 22. Due to the screw-threaded engagement between the pinion carrier 13 and the drive sleeve 22, the drive sleeve will now move to the right until it abuts against the inner end of the disengagement sleeve 26.

Since the starting motor'M cannot accelerate immediately to the velocity of ring gear 12, the pinion carrier 13 now will be forced to the left along shaft 10 because of the screw-threaded engagement between the pinion carrier and the sleeve 22, which is now restrained against further movement to the right by the disengagement sleeve 26. This inertia-operated movement of th pinion carrier 13 to the left takes place against the magnetic force exerted by the still-energized solenoid 21 which is acting on the pinion carrier through the armature 20 and linkage 19. The force exerted by the leftward-moving pinion carrier 13 against the solenoid arenergized, its return spring insures the completion of the movement of the solenoid armature 20 to its fully extended position. Such movement of the armature 20, acting through the linkage 19, causes the continued movement of the sleeve 15, pinion carrier 13 and pinion I1 to the left in FIG. 1 until the pinion is completely disengaged from the ring gear 12 and the sleeve 15 is thrust frictionally against the'brake washer 29. This frictional restraint slows down the rotation of the sleeve 15, pinion carrier 13 and pinion 11 to a speed below that of shaft 10 and drive sleeve 22. Consequently, at this time, because of the screw-threaded engagement between the pinion carrier 13 and the drive sleeve 22, the drive sleeve will move to the left along the pinion carrier until its again engages the latters internal shoulder 25, at which time the drive sleeve 22 and shaft 10 are braked to a stop along with the sleeve 15, pinion carrier 13 and pinion 11.

Referring to FIG. 2, the electrical control circuit in the present starting system includes a normally-open ignition switch 30 connected in series with the vehicle load and engine ignition circuit 31 across a direct current power source, such as the vehicle battery 32.

The starting motor M is connected in series with a set of normally-open solenoid contacts 33 across the power source 32. Contacts 33 are closed when the armature 20 is pulled in by the solenoid 21, when the solenoid is energized and at a time when the meshing engagement of the pinion 11 with the ring gear 12 is assured.

The solenoid is connected in series with a normallyopen, push-button, starting switch 34 and a set of normally-closed contacts 35, 36 across the power source 32.

A first coil 37 for opening the contacts 36, 35 is connected in series with a semiconductor rectifier 38 between the ignition switch and the solenoid contacts 33. When energized, coil 37 moves the mobile contact 36 away from the fixed contact 35 and into engagement with a fixed contact 39 connected to the juncture 40 between coil 37 and the anode of rectifier 38.

A second coil 41 is connected in parallel with the starting motor M and when energized it closes a set of normally-open contacts 42, 43. The fixed contact 43 of this set is connected to the starting switch 34, and the mobile contact 42 is connected directly to the mobile contact 36 and to the negative terminal of battery 32.

In the operation of this control circuit, when the operator closes the push-button switch 34, this completes an energization circuit for the solenoid 21 by way of the set of normally-closed contacts 35, 36. When energized, solenoid 21 pulls in its armature 20 to close the solenoid contacts 33 and thereby complete an energization circuit for the starting motor M. At the same time, as described with reference to FIG. 1, the energization of solenoid 21 causes the pinion 11 to be moved into meshing engagement with the ring gear 12.

Also, the closing of the solenoid contacts 33 completes the energization circuit for coil 41, which closes its contacts 42, 43 to provide a holding circuit for maintaining solenoid 21 energized independent of contacts 35 and 36. However, it is to be understood that the continued energization of the solenoid depends upon the driver's holding the starting switch 34 closed.

Now, when the vehicle driver closes the ignition switch 30 to start the vehicle engine, the coil 37 is energized through the ignition switch, rectifier 38 and the now-closed solenoid contacts 33. Coil 37, when thus energized, opensits contacts 36, 35 and closes'its contacts 36, 39 to complete a holding circuit foritself which is independent of the solenoid contacts 33.

After the vehicle engine has reached a certain speed, as described,'.to cause the pinion carrier 13 to force the solenoid armature 20 toward its extended position (against the magnetic force exerted on it by the stillenergized solenoid 21), the opening of the solenoid contacts 33 breaks the energization circuit for the starting motor M and coil 41. When coil 41 is de-energized, its contacts 42, 43 re-open, breaking the holding circuit for solenoid 21, so that solenoid 21 now is de-energized and cannot be re-energized while coil 37 remains energized, which condition prevails as long as the ignition switch 30 for the vehicle engine remains closed. Consequently, the driver cannot re-start the starting motor M as long as the vehicle engine remains running.

From the foregoing description it will be evident that the disclosed embodiment of the present engine starting system provides solenoid-operated positive engagement of the starting motor-driven pinion with the ring gear connected to the engine, inertia-operated disengagement of the pinion from the ring gear once the engine begins to overrun the starting motor, and a novel control arrangement which insures that once the pinion is disengaged it cannot be re-engaged as long as the engine ignition switch remains closed.

While a presently-preferred embodiment of this starting system has been described in detail with reference to the accompanying drawing, it is to be understood that various modifications, omissions and adaptations which depart from the disclosed embodiment may be adopted without departing from the scope of the present invention.

Having described my invention, I claim:

1. An engine starting apparatus comprising a starting motor, a rotary shaft driven by said starting motor, a pinion carrier shiftable axially along said shaft, a pinion carried by said pinion carrier for rotation therewith and for movement thereby into or out of driving engagement with a gear coupled to the engine, and a drive member coupled to said shaft for rotation in unison therewith and for movement in either direction along the shaft, said drive member being screw-threadedly coupled to said pinion carrier, and limit stops for limiting the movement of said drive member in each direction along said shaft, and wherein one of said limit stops is a transverse shoulder in the pinion carrier, and wherein the inertia force on the pinion, which initially opposes rotation of the pinion and the pinion carrier in unison with the shaft when the pinion meshes with the gear, through the screw-threaded engagement between the pinion carrier and said drive member forces the drive member against said shoulder to impart the rotation of the shaft to the pinion carrier, and wherein the inertia force on the shaft, when the pinion begins to rotate faster than the shaft, through the screw-threaded engagement between the pinion carrier and said drive member causes the drive member to move away from said shoulder along the shaft until it engages the other of said limit stops, after which said last-mentioned inertia force causes the pinion carrierto move in the opposite direction along the shaft to disengage the pinion from said gear.

. 2. An engine starting apparatus comprising a starting motor, a rotary shaft driven by said starting motor, a pinion carrier shiftable axially along said shaft, a pinion carried by said pinion carrier for rotation therewith and for movement thereby into or out of driving engagement with a gear coupled to the engine, a drive member coupled to said shaft for rotation in unison therewith and for movement in either direction along the shaft, said drive member being screw-threadedly coupled to said-pinion carrier, limit stops for limiting the movement of said drive member in each direction along said shaft, and actuator means for moving said drive member, pinion carrier and pinion together along said shaft from a first position in which said pinion is spaced from said gear to a second position in which said pinion engages said gear.

3. A starting system according to claim 2, wherein the inertia force on the pinion, when the latter engages said gear and said shaft begins to rotate, initially opposes rotation of the pinion and the pinion carrier in unison with the shaft and through the screw-threaded engagement between the pinion carrier and said drive member causes the drive member, while rotating with the shaft, to move along said shaft until it engages one of said limit stops, after which the drive member imparts the rotation of the shaft to "the pinion carrier.

4. A starting system according; to claim 2, wherein the inertia force on said shaft, when the pinion begins to rotate faster than the shaft, through the screwthreaded engagement between the pinion carrier and said drive member causes the drive member to move along said shaft until it engages one of said limit stops,

after which said inertia force causes the pinion carrier to move along said shaft to disengage the pinion from said gear.

5. A starting apparatus according to claim 1, wherein said pinion carrier is an annular body extending around said shaft and having an internally screw-threaded portion, and said drive member is a sleeve splined to said shaft and having an externally screw-threaded portion which drivingly engages said internally screw-threaded portion of the pinion carrier.

6. A starting apparatus according to claim 2, wherein said pinion is coupled to said pinion carrier for turning movement therewith to facilitate meshing engagement of the pinion with said gear, and further comprising spring means urging said pinion to a predetermined position axially along said pinioncarrier.

7. An engine starting apparatus for use in association with a cranking motor, said apparatus comprising a rotatable shaft adapted to be driven by the cranking motor, a pinion gear movable along; said shaft between a retracted position spaced from a second gear coupled to the engine and a driving position engaging said second gear, a carrier member, first connector means for transmitting drive forces between said pinion gear and carrier member, a drive member, second connector means for transmitting drive forces between said drive member and said shaft and for enabling said drive member to move axially along said shaft while preventing rotation of said drive member relative to said shaft, actuator means for moving said carrier member, drive member and pinion gear in a first direction along said shaft to effect movement of said pinion gear from the retracted position to the driving position, first thread convolution means connected with said carrier member and second thread convolution means connected with said drive member and disposed in engagement with said first thread convolution means, said first and second threadconvolution means being operable to.

move said carrier member and pinion gear in a second direction along said shaft in response to starting of the engine to move said pinion gear from the driving position toward the retracted position.

8. An engine starting apparatus as set forth in claim 7 further including first stop means for limiting movement of said drive member along said shaft in the first direction and second stop means movable with said carrier member relative to said shaft for limiting movement of said drive member in the second direction.

9. An apparatus as set forth in claim 7 wherein said actuator means includes means for continuing movement of said carrier member and pinion gear in the second direction along said shaft to move said pinion gear to the retracted position after said first and second thread convolution means initiate movement of said pinion gear from the driving position toward the retracted position in response to starting of the engine.

10. An apparatus as set forth in claim 7 wherein said actuator means includes a movable armature member connected with said carrier member, drive member and pinion gear, and means for providing an electromagnetic field to effect movement of said armature member to move said carrier member, drive member and pinion gear in the first direction along said shaft, said first and second thread convolution means being effective to move said armature member against the influence of the magnetic field as said pinion gear is moved from the driving position toward the retracted position in response to starting of the engine.

11. An engine starting apparatus for use in association with a cranking motor, said apparatus comprising a shaft adapted to be rotated by the cranking motor, a pinion gear, and means for connecting the pinion gear with said shaft and for moving said pinion gear between a retracted position in which said pinion gear is spaced from a second gear coupled to the engine and a driving position in which said pinion gear engages said second gear, said means including a carrier member connected with the pinion gear, a first set of thread convolutions connected with said carrier member, a drive member disposed in sliding engagement with said shaft, means for transmitting force from said shaft to said drive member during rotation of said shaft under the influence of the cranking motor, a second set of thread convolutions connected with said drive member and disposed in engagement with said first set of thread convolutions, means for defining a first stop surface, means for rotating said carrier member relative to said shaft and drive member to effect relative rotation between said first and second sets of thread convolutions in one direction to move said drive member in a first direction along said shaft and into engagement with said first stop surface in response to starting of the engine and for continuing the rotation of said carrier member relative to said drive member after said drive member engages said first stop surface to move said carrier member and pinion gear along said shaft in a second direction opposite to said first direction and effect movement of said pinion gear from the driving position toward the retracted position, and brake means for retarding rotation of said carrier member upon movement of said pinion gear to the retracted position to effect relative rotation between said first and second sets of thread convolutions in a direction opposite to said one direction to move said drive member in the second direction along said shaft after said pinion gear moves to the retracted position.

12. An engine starting apparatus as set forth in claim 11 further including means connected to said carrier member for defining a second stop surface movable with said carrier member along said shaft, said first and second stop surfaces being spaced apart by a first distance when said pinion gear is in the retracted position and being spaced apart by a second distance which is smaller than said first distance when said pinion gear is in the driving position. 

1. An engine starting apparatus comprising a starting motor, a rotary shaft driven by said starting motor, a pinion carrier shiftable axially along said shaft, a pinion carried by said pinion carrier for rotation therewith and for movement thereby into or out of driving engagement with a gear coupled to the engine, and a drive member coupled to said shaft for rotation in unison therewith and for movement in either direction along the shaft, said drive member being screw-threadedly coupled to said pinion carrier, and limit stops for limiting the movement of said drive member in each direction along said shaft, and wherein one of said limit stops is a transverse shoulder in the pinion carrier, and wherein the inertia force on the pinion, which initially opposes rotation of the pinion and the pinion carrier in unison with the shaft when the pinion meshes with the gear, through the screw-threaded engagement between the pinion carrier and said drive member forces the drive member against said shoulder to impart the rotation of the shaft to the pinion carrier, and wherein the inertia force on the shaft, when the pinion begins to rotate faster than the shaft, through the screwthreaded engagement between the pinion carrier and said drive member causes the drive member to move away from said shoulder along the shaft until it engages the other of said limit stops, after which said last-mentioned inertia force causes the pinion carrier to move in the opposite direction along the shaft to disengage the pinion from said gear.
 2. An engine starting apparatus comprising a starting motor, a rotary shaft driven by said starting motor, a pinion carrier shiftable axially along said shaft, a pinion carried by said pinion carrier for rotation therewith and for movement thereby into or out of driving engagement with a gear coupled to the engine, a drive member coupled to said shaft for rotation in unison therewith and for movement in either direction along the shaft, said drive member being screw-threadedly coupled to said pinion carrier, limit stops for limiting the movement of said drive member in each direction along said shaft, and actuator means for moving said drive member, pinion carrier and pinion together along said shaft from a first position in which said pinion is spaced from said gear to a second position in which said pinion engages said gear.
 3. A starting system according to claim 2, wherein the inertia force on the pinion, when the latter engages said gear and said shaft begins to rotate, initially opposes rotation of the pinion and the pinion carrier in unison with the shaft and through the screw-threaded engagement between the pinion carrier and said drive member causes the drive member, while rotating with the shaft, to move along said shaft until it engages one of said limit stops, after which the drive member imparts the rotation of the shaft to the pinion carrier.
 4. A starting system according to claim 2, wherein the inertia force on said shaft, when the pinion begins to rotate faster than the shaft, through the screw-threaded engagement between the pinion carrier and said drive member causes the drive member to move along said shaft until it engages one of said limit stops, after which said inertia force causes the pinion carrier to move along said shaft to disengage the pinion from said gear.
 5. A starting apparatus according to claim 1, wherein said pinion carrier is an annular body extending around said shaft and having an internally screw-threaded portion, and said drive member is a sleeve splined to said shaft and having an externally screw-threaded portion which drivingly engages said internally screw-threaded portion of the pinion carrier.
 6. A starting apparatus according to claim 2, wherein said pinion is coupled to said pinion carrier for turning movement therewith to facilitate meshing engagement of the pinion with said gear, and further comprising spriNg means urging said pinion to a predetermined position axially along said pinion carrier.
 7. An engine starting apparatus for use in association with a cranking motor, said apparatus comprising a rotatable shaft adapted to be driven by the cranking motor, a pinion gear movable along said shaft between a retracted position spaced from a second gear coupled to the engine and a driving position engaging said second gear, a carrier member, first connector means for transmitting drive forces between said pinion gear and carrier member, a drive member, second connector means for transmitting drive forces between said drive member and said shaft and for enabling said drive member to move axially along said shaft while preventing rotation of said drive member relative to said shaft, actuator means for moving said carrier member, drive member and pinion gear in a first direction along said shaft to effect movement of said pinion gear from the retracted position to the driving position, first thread convolution means connected with said carrier member and second thread convolution means connected with said drive member and disposed in engagement with said first thread convolution means, said first and second thread convolution means being operable to move said carrier member and pinion gear in a second direction along said shaft in response to starting of the engine to move said pinion gear from the driving position toward the retracted position.
 8. An engine starting apparatus as set forth in claim 7 further including first stop means for limiting movement of said drive member along said shaft in the first direction and second stop means movable with said carrier member relative to said shaft for limiting movement of said drive member in the second direction.
 9. An apparatus as set forth in claim 7 wherein said actuator means includes means for continuing movement of said carrier member and pinion gear in the second direction along said shaft to move said pinion gear to the retracted position after said first and second thread convolution means initiate movement of said pinion gear from the driving position toward the retracted position in response to starting of the engine.
 10. An apparatus as set forth in claim 7 wherein said actuator means includes a movable armature member connected with said carrier member, drive member and pinion gear, and means for providing an electromagnetic field to effect movement of said armature member to move said carrier member, drive member and pinion gear in the first direction along said shaft, said first and second thread convolution means being effective to move said armature member against the influence of the magnetic field as said pinion gear is moved from the driving position toward the retracted position in response to starting of the engine.
 11. An engine starting apparatus for use in association with a cranking motor, said apparatus comprising a shaft adapted to be rotated by the cranking motor, a pinion gear, and means for connecting the pinion gear with said shaft and for moving said pinion gear between a retracted position in which said pinion gear is spaced from a second gear coupled to the engine and a driving position in which said pinion gear engages said second gear, said means including a carrier member connected with the pinion gear, a first set of thread convolutions connected with said carrier member, a drive member disposed in sliding engagement with said shaft, means for transmitting force from said shaft to said drive member during rotation of said shaft under the influence of the cranking motor, a second set of thread convolutions connected with said drive member and disposed in engagement with said first set of thread convolutions, means for defining a first stop surface, means for rotating said carrier member relative to said shaft and drive member to effect relative rotation between said first and second sets of thread convolutions in one direction to move said drive member in a first direction along said Shaft and into engagement with said first stop surface in response to starting of the engine and for continuing the rotation of said carrier member relative to said drive member after said drive member engages said first stop surface to move said carrier member and pinion gear along said shaft in a second direction opposite to said first direction and effect movement of said pinion gear from the driving position toward the retracted position, and brake means for retarding rotation of said carrier member upon movement of said pinion gear to the retracted position to effect relative rotation between said first and second sets of thread convolutions in a direction opposite to said one direction to move said drive member in the second direction along said shaft after said pinion gear moves to the retracted position.
 12. An engine starting apparatus as set forth in claim 11 further including means connected to said carrier member for defining a second stop surface movable with said carrier member along said shaft, said first and second stop surfaces being spaced apart by a first distance when said pinion gear is in the retracted position and being spaced apart by a second distance which is smaller than said first distance when said pinion gear is in the driving position. 